LateInitializationError: Field 'insertFunction has not been initialized

Question

我是 Flutter 的新手，实际上 stuck.I 我正在尝试创建一个搜索功能，使用关键字调用我的 Sqfite 数据库中的列表。数据库一切正常，但是当我在搜索栏中插入关键字时，应用程序的一部分崩溃并出现以下错误：

LateInitializationError: Field 'insertFunction' 尚未 initialized.Im 使用 insertFunction 和 deleteFunction 参数和构造函数，但我的 createState 抛出一个错误，然后它需要 insert 和 deleteFunction 数据，我不能这样做因为不能将逻辑传递到 createState。

任何帮助将不胜感激。我需要解决我的 createState 问题和 Lateinitialization 问题。

代码如下：

class SearchPage extends StatefulWidget {
 @override
  _SearchPageState createState() => _SearchPageState();//createState is throwing an error and 
                                                       as that I insert insertFunction and 
                                                       deleteFunction here. But if i do, it 
                                                      also say I should not put logic into 
                                                      createState. 
         }

   class _SearchPageState extends State<SearchPage> {
   late final Function insertFunction;
   late final Function deleteFunction;
   var db = DatabaseConnect();
   String keyword = '';

      _SearchPageState({required this.insertFunction,required this.deleteFunction,});

       @override
       Widget build(BuildContext context) {

       return Scaffold(
        appBar: AppBar(
        title: const Text('Search My Clients'),
          leading: GestureDetector(
           onTap: () {
           Navigator.of(context).pushReplacementNamed('/homePage');
          },
          child: const Icon(
          Icons.arrow_back,
           ),
         ),
        ),
        body: SingleChildScrollView(
         child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
           Padding(
            padding: const EdgeInsets.all(15.0),
            child: TextField(
            autofocus: true,
             decoration: const InputDecoration(
                border: OutlineInputBorder(),
                labelText: 'keyword',
                prefixIcon: Icon(Icons.search)),
                onChanged: (value) {
                keyword = value;
                 setState(() {});
                },
               ),
             ),
              FutureBuilder(
               future: db.searchContacts(keyword),
                builder: (context, AsyncSnapshot<List> snapshot) {
                if (snapshot.hasError) const Text('error');
                var data = snapshot.data;
                var datalength = data!.length;

                 if (snapshot.hasData) {
                 return datalength == 0
                    ? const Center(
                        child: Text('no data found'),
                      )
                    : Container(
                        child: LimitedBox(
                          maxHeight: 200,
                          child: ListView.builder(
                            scrollDirection: Axis.vertical,
                            itemCount: datalength,
                            shrinkWrap: true,
                            itemBuilder: (context, i) => CustomerCard(
                              id: data[i].id,
                              title: data[i].title,
                              name: data[i].name,
                              phone: data[i].phone,
                              fax: data[i].fax,
                              email: data[i].email,
                              street: data[i].street,
                              city: data[i].city,
                              town: data[i].town,
                              code: data[i].code,
                              isExpanded: data[i].isExpanded,
                              insertFunction: insertFunction,
                              deleteFunction: deleteFunction,
                            ),
                          ),
                        ),
                      );
                        } else {
                        return const Center(
                       child: Text('no data found'),
                              );
                             }
                           }),
                           ],
                          ),
                          ),
                        );
                       }
                    }

Answer 1

这就是您的代码应有的样子

class SearchPage extends StatefulWidget {
@override
  _SearchPageState createState() => _SearchPageState(); 
}

class _SearchPageState extends State<SearchPage> {
  insertFunction(){
    //function body goes here
  } 

  deleteFunction(){
    //function body goes here
  }

  var db = DatabaseConnect();
  String keyword = '';
  //the rest goes here

LateInitializationError: Field 'insertFunction has not been initialized

LateInitializationError: Field 'insertFunction has not been initialized

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lazy-initialization

flutter